Hydrocarbon production wells which are drilled in the earth to produce oil or gas must be reworked or serviced from time to time. Wells may require service for a number of reasons. For example, worn or faulty valves may require replacement, seals may need to be replaced or renewed, or it may be necessary or desirable to insert a new flange or remove a flange from the wellhead, etc. Well workover generally entails well treatments to stimulate hydrocarbon production. Such treatments may include high pressure fracturing and/or acidizing. During well stimulation it is common knowledge that it is preferable to introduce stimulation fluids into the well at the highest possible transfer rate. Consequently, the wellhead is now frequently removed and stimulation fluids are pumped through the blowout preventers and into the casing. In order to protect the blowout preventers, blowout preventer protectors have been invented, as described in Applicant's U.S. Pat. No. 5,819,851 which issued on Oct. 13, 1998. Generally, a workover rig is brought in and setup to remove the wellhead components when well workover is required. Such rigs comprise a derrick or mast which supports pulleys or block and tackle arrangements operable to pull the wellhead from the well and may also be used to pull the production tubing string from the well bore or run a production tubing string or other tools into the well.
The rig is used to remove and replace the wellhead, unseat and reseat the packers and/or anchors in the well, etc. Although workover rigs are functional and adapted to perform any job associated with manipulating well components during a well workover, they are large assemblies of equipment that are expensive to move and setup. Besides, they require a crew of four, so they are expensive to operate.
A workover rig may also be brought in for servicing a well to install blowout preventers (BOPs), repair or replace valves or seals, etc. In each of these servicing operations the production tubing is not removed from or run into the well. Nonetheless, the production tubing may have to be lifted with the wellhead.
Efforts have been made to develop various types of lifting apparatus for use in well workovers and well servicing operations. In particular, a portable or compact apparatus has been invented for replacing a large conventional well rig for lifting a wellhead and production tubing string in certain well servicing or workover applications. U.S. Pat. No. 4,756,366 which issued to Maroney et al. on Jul. 12, 1988 and is entitled "WELL SERVICING METHODS USING A HYDRAULIC ACTUATED WORKOVER MAST", discloses a portable workover rig for lowering and raising objects such as pipe into and out of a borehole. The workover rig is mounted to a heavy vehicle and includes a mast which can be raised from a horizontal to a vertical position, a hydraulic system and drum cable system. Nevertheless, the portable workover rig disclosed in this patent is expensive to construct and operate because a dedicate vehicle, a dedicated hydraulic system and a complicated mechanical structure are involved.
A tool useful in pulling casing from a dead well is illustrated in U.S. Pat. No. 2,661,063, which issued to Owens on Dec. 1, 1953 and is entitled "METHOD AND MEANS OF PULLING PIPE FROM A WELL". Owens discloses the use of a pair of hydraulic jacks to loosen a pipe that gets stuck while being pulled from a dead well by a rig. The jacks exert an upward force through two arms affixed to a collar attached by shearable pins to the pipe being pulled by the rig. The pins shear unless the pipe dislodges from the stuck position. The shearing of the pins causes a downward jar or jerk on the pipe that tends to loosen the pipe. After the pipe is loosened, it is pulled from the well using the rig until it is removed, or it gets stuck again. It is apparent that the jacks used in this application are auxiliary and only used in conjunction with a rig. The jacks are not designed to lift a wellhead for well servicing or workover. Nor is the pipe being lifted by the jacks rotatable relative to the collar due to the shearable pin connection between the two. Therefore, this apparatus is not adapted for well servicing or workover.
There therefore exists a need for a safe, economical apparatus for well servicing or workover which permits a servicing or workover operation to be rapidly and efficiently accomplished when tubing does not need to be run into or removed from the well.